How the mummified “mountain witches” of Japan blurred the line between relic, hoax and holy object

In a handful of quiet mountain temples in Japan, glass cases hold something that looks like it belongs in a horror film: shriveled “mermaid” bodies, tiny horned skulls and dried creatures said to be tengu or mountain goblins. Locals sometimes call them “yama no obake” or “mountain spirits,” visitors call them creepy, and historians see them as a window into a different way of thinking about belief and evidence.

These strange relics are part hoax, part devotional object and part folk museum. By tracing how they were made, displayed and understood, we get a surprisingly practical lesson in how people in the past handled uncertainty, mixed faith with entertainment and coped with a dangerous natural world.

What are Japan’s “mountain witches” and other yokai mummies?

Across Japan, especially in older temples and rural museums, you can sometimes find “mummies” said to be mermaids, kappa (river imps), tengu (beaked mountain goblins) or other yokai, the broad category of Japanese spirits and monsters. Most are small, rarely longer than a child’s arm, and clearly not human on close inspection.

Many were made from stitched-together animal parts: a monkey torso joined to a fish tail, or a carved wooden beak added to a skull. Some are simple dried animals presented as something more mysterious. Others are elaborate works of taxidermy art. Their age and exact origin often remain uncertain, and modern researchers usually approach them with a mix of skepticism and curiosity.

Why anyone wanted a fake mermaid mummified in their temple

These hybrids did not usually begin as cynical cons. In early modern Japan, from the 17th to the 19th century, people lived with frequent disasters, limited medical knowledge and a complex religious landscape. Objects that hinted at the supernatural could serve several roles at once: souvenirs, warnings, protective charms and entertaining curiosities.

Some “mermaid mummies” were promoted as moral lessons. Stories circulated that seeing such a creature could remind people of the impermanence of life or the danger of greed. In other cases, a temple might receive a strange object as a donation from a wealthy traveler or merchant. Placed on display, it drew visitors, who then donated money, prayed and listened to sermons.

How yokai mummies were actually made

While each relic is unique, historians and conservators who have examined them up close tend to find practical craftwork rather than true mystery. Techniques varied, but some common patterns appear:

• Composite bodies:Monkey, fish, bird and small mammal parts were cleaned, dried and carefully sewn together, often with concealed seams and added papier-mâché.
• Artificial aging:Surfaces were smoked, stained or lacquered to darken and harden the “skin,” helping stitched areas blend in and creating a uniform mummified look.
• Carving and modeling:Teeth, claws, horns and beaks were sometimes carved from wood or bone, then attached and painted to look natural.
• Story packaging:The object was given a label, a tale of discovery and sometimes a written charm or explanatory scroll that framed how viewers should understand it.

These makers were not amateur pranksters. Many seem to have been highly skilled artisans familiar with both taxidermy and religious imagery. In some cases, their work resembles the fine detail seen in netsuke or other miniature carvings, just applied to something meant to look unsettling rather than beautiful.

Belief, doubt and the polite acceptance of the strange

The people who first encountered these mummies were not necessarily gullible. Prints and popular literature of the time often poked fun at obvious fakes, and some writers openly described the process of making such creatures. Curiosity and amusement were part of the appeal.

At the same time, certainty was not always required. A relic could be “as if” real: perhaps no one could prove that mermaids existed, but they symbolized distant oceans, unknown dangers and the possibility of hidden truths. A visitor might look, shiver a little, offer a coin and move on without demanding a clear answer.

Temple officials also showed a flexible attitude. Some catalogued their mummies as “traditionally said to be a mermaid” or “believed by locals to be a kappa,” carefully using language that reported belief without fully endorsing it. The power of the object lay less in factual accuracy and more in the feelings and stories it generated.

What modern science has (and has not) solved about them

In the last few decades, a few of these relics have been examined with modern tools. Where owners have allowed it, researchers have taken small samples for DNA testing, X-rayed internal structures or used endoscopes to look inside fragile bodies without opening them.

Results vary, but they generally support the composite-creation explanation. One widely discussed “mermaid” was found to contain parts from several fish species, bits of mammal bone and a wooden frame. Another supposed tengu had a human-made interior structure wrapped in animal hide. Detailed scientific publications for each specimen are still limited, and access can be sensitive because temples worry about damaging objects or undermining long-held local traditions.

Importantly, even when a mummy is thoroughly debunked as a natural creature, that does not end its historical value. Instead, the focus shifts from “Is this real?” to “How and why did people make this?” and “What did it mean to those who kept it safe for centuries?”

What these “mountain witches” reveal about their time

Look past the claws and twisted faces, and these relics tell us several useful things about life and thought in earlier Japan. First, they show how tightly entertainment and religion could be interwoven. A visit to a temple might combine prayer, scenic viewing, small snacks and a peek at a weird mummy, without any clear boundary between serious and playful moments.

Second, they highlight the role of physical objects in making the invisible feel tangible. Spirits, monsters and protective forces are hard to imagine in the abstract. A dried, uncanny body in a case gave form to anxieties about storms, illness or getting lost in the mountains, and made ritual responses to those fears feel more concrete.

Third, they remind us that “fake” does not always mean “meaningless.” The makers likely knew they were assembling animals, but they were also responding to a market for objects that expressed curiosity about the world, flirted with the taboo and fit into existing belief systems. Their work is closer to theater props than pure fraud.

How to visit responsibly if you ever see one

If you travel in Japan and notice a sign for a ningyo (mermaid) mummy or a tengu relic, it may be possible to visit respectfully, depending on local rules. These sites are often small, active religious spaces rather than big tourist attractions, so a bit of care goes a long way.

• Ask before taking photos, especially inside halls and near altars.
• Treat the object as the community does, whether that means quiet curiosity, a lighthearted look or a brief bow.
• Read any available explanation panels, which often make clear whether the item is seen as a legend, a confirmed composite or something in between.
• Remember that for locals, the story around the mummy may matter more than its biological origin.

Seen in this way, Japan’s “mountain witches” and yokai mummies stop being just oddities in a cabinet. They become carefully preserved records of how real people once mixed fear, faith and creativity, and how they tried to make sense of a world full of hazards that felt as mysterious as any monster.